The present invention relates to a pipe or the like, of the type comprising:                a concrete cylinder possessing at least one annular end of determined longitudinal axis, defined in particular by a longitudinal outside peripheral face and by a transverse front face;        a female end ring coaxial with said end and secured thereto, the ring consisting in:                    firstly a longitudinal ferrule for securing to the cylinder, the ferrule being defined in particular by a longitudinal inside peripheral face fitting snugly against said outside peripheral face in the immediate vicinity of said front face; and            secondly a longitudinal skirt projecting longitudinally over said front face to engage coaxially on a male endpiece of another pipe or the like.                        
The term “the like” as used herein with respect to pipes means building elements and ducts that can be assembled by being engaged mutually, such as galleries, access holes, so-called “ovoid” interfittable ducting, ducts of the type sold under the registered trademark “MODULOVALE”, and shelter modules, with these examples not being limiting in any way, providing said outside peripheral face presents a cross-section that is curved and convex, either in usual manner or else following simple adaptation in order to implement the present invention.
Similarly, the term “concrete” should be understood herein in its most general sense, covering in particular both concrete based on resin and concretes based on a mineral binder.
In the present state of the art, the female end ring made of metal or of synthetic material is usually fastened to the cylinder by overmolding the cylinder directly onto the ferrule. By way of example, such a technique is described for a female end ring of synthetic material in British patent application No. 2 217 418, which also mentions the possibility of fixing the ring on the cylinder after the cylinder has been made, probably by using a cement given the complexity of some of the shapes described.
The fastening obtained in that way between the female end ring and the cylinder can be satisfactory providing the precaution is taken of shaping the ferrule in such a manner as to obtain mutual anchoring via complementary shapes, however whatever precautions are taken in this respect, sealing between the ferrule and the cylinder remains problematic, even if sealing is defined merely as an absence of any visible seepage of a liquid placed at a pressure close to ambient pressure going from one side to the other of the gasket between the ferrule and the cylinder.
Proposals have also been made, in U.S. Pat. No. 5,180,196, and specifically with reference to FIG. 6 of that document, to make a female endpiece on a longitudinal concrete cylinder by longitudinally engaging a ferrule-forming zone of a longitudinal female end ring on an outside peripheral face at one annular end of the cylinder under conditions such that another zone of the ring forms a skirt projecting longitudinally from the front face of the cylinder for receiving internally a pipe of different design.
Sealing between the ferrule of the female end ring and the outside peripheral face at the end of the cylinder is then provided by two transverse annular bands that are tightened by screws, locally surrounding the ferrule and locally pressing against the outside peripheral face at the end of the cylinder, thus also providing mutual fastening by friction between the cylinder and the female end ring.
The use of such bands can limit the applications of the pipe or the like made in that way in that the material from which the bands are made, which material is dictated by considerations of a mechanical nature, can be incompatible with certain installation conditions for the pipe or the like. Thus, as a general rule, bands are made of steels of a grade that is selected as a function of criteria concerning traction strength and modulus of elasticity, but such seals are generally vulnerable to corrosion and are consequently unusable whenever the pipes or the like are to be buried (unless they are subjected to additional anti-corrosion protection and/or treatment which is expensive and of short-term effectiveness).
In addition, the effectiveness of the sealing and the fastening between the ferrule of the female end ring and the outside peripheral face at the end of the cylinder then depends on the magnitude of the transverse pressure between them, which in turn depends on the value of the transverse pressure applied by the annular bands to the outside of the ferrule, and consequently to a circumferential tension given to the annular bands by screw-tightening.
Unfortunately, the pressure applied by the bands to the ferrule gives rise to transverse thrust pressure from the ferrule of the female endpiece on the outside peripheral face at the end of the cylinder only through the ferrule, making it necessary to ensure that the ferrule tends to shrink onto the outside peripheral face of the end of the cylinder from a rest condition in which it is engaged on said outside peripheral face.
The ferrule has a natural tendency to oppose such shrinkage from its rest condition so obtaining mutual transverse thrust pressure between the ferrule of the female end ring and the outside peripheral face of the cylinder with sufficient magnitude to ensure effective sealing between them and also to ensure that they are effectively fastened together requires a considerable amount of pressure to be developed between the bands and the ferrule by putting the bands under circumferential tension at the risk of causing irremediable damage to the ferrule.
In practice, the desire to avoid any risk of such damage leads to the magnitude of the circumferential tension in the bands and of the pressure they apply to the ferrule being limited, and the tendency of the ferrule to oppose shrinkage means that the magnitude of the transverse thrust pressure actually applied by the ferrule to the outside peripheral face of the cylinder is even smaller, i.e. not only is fastening between them ineffective, but also the resulting sealing is doubtful.